In vitro and in vivo comparison of platelet concentrates collected by automated versus manual apheresis

Platelet concentrates derived from buffy coat and apheresis: biochemical and functional differences

Today, platelet concentrates are generally produced from whole blood by differential centrifugation (buffy coat-derived platelet concentrates--PCs) or by plateletpheresis (apheresis-derived platelet concentrates--APCs). As PCs are characterized by a lower number of platelets than APCs, four to six PCs are customarily combined in order to obtain an equivalent dose. In the 1970s and 1980s, the use of PCs exceeded that of APCs by far; in contrast, since the beginning of the 1990s, APCs comprise more than half of all transfused platelets. However, the selection of PCs or APCs for transfusion to thrombocytopenic patients is still a matter of debate. The present paper compares biochemical and functional properties of both platelet preparations in vitro. Besides plasma parameters (e.g. platelet factor 4 (PF4), P-selectin, C3a-desarginin, plasma coagulation factors), platelet function was analysed by aggregometry and the PFA 100 system. APCs are characterized by a better preservation of ADP and collagen-induced platelet aggregation, and shorter closure times of the PFA 100 test system during storage. The improved primary in vitro haemostatic capacity of APCs is presumed to be owing to a lower cellular activation rate in these preparations. This hypothesis is supported by the higher plasma concentrations of PF4, beta-thromboglobulin and P-selectin found in PCs compared with APCs. The concentrations of C3a-desarginin in PCs exceed those in APCs by far. Additionally, thrombin generation is higher in PCs than in APCs. These data suggest that APCs are characterized by a superior haemostatic capacity over PCs in vitro. However, in vivo studies should be performed to confirm these findings in the patients' circulation also.

Viability of platelets collected by apheresis versus the platelet-rich plasma technique: a direct comparison

Different platelet preparation techniques have not previously been compared directly and simultaneously with respect to in vivo platelet viability. Using a dual-label technique with 111-In and 114m-In, platelet apheresis was compared with the platelet-rich plasma (PRP) procedure with respect to platelet recovery and survival (n=4). Furthermore, a continuous flow cell separator (Cobe 2997) and an intermittent apheresis system (Haemonetics V50) were compared with each other (n=4). No differences in platelet viability were found between the PRP-platelets and the apheresis-platelets. Also no differences were found between the two apheresis systems. Although different platelet preparation methods result in a varying degree of platelet activation, no difference in platelet viability has been observed.

Platelet concentrates in an additive solution prepared from pooled buffy coats. In vivo studies

Leukocyte-depleted platelet concentrates were prepared from pools of 4 buffy coats on the day after blood collection (BC-PC). The storage medium was composed of citrate phosphate dextrose plasma and a platelet-additive solution. Autologous transfusions of 111In-labelled platelets in 9 healthy volunteers were performed on the day of preparation (day 1) and on day 5. The recovery was 54.6 +/- 8.7 (day 1) and 51.9 +/- 10.4% (day 5), T1/2 was 101 +/- 28 and 61 +/- 9 h, respectively. The survival was 8.3 +/- 1.7 and 5.7 +/- 1.0 days, respectively, using linear plot, and 7.8 +/- 2.0 and 5.8 +/- 0.5 days using the multiple hit method. In a prospective clinical study a comparison of the corrected posttransfusion increments was made between BC-PCs and apheresis-PC, and between fresh (1-2 days) and stored (3-5 days) preparations. No difference was found between BC-PCs and apheresis PCs. However, fresh BC-PCs gave higher increments than stored BC-PCs. A slight numerical difference between fresh and stored apheresis-PCs was not statistically significant. It is concluded that the BC-PC method results in platelets of equal quality to apheresis-PC.